Changes Of Water Uptake By Roots And Its Mechanism During The Replacement Process Of Dry-land Winter Wheat

Wheat is one of the most important food crops in the world.Wheat production in arid and semi-arid areas is severely restricted by water shortages,which will affect future food security.Winter wheat varieties in the Loess Plateau have undergone a change from ancient farm varieties to modern dwarf wheat varieties,and their productivity has been greatly improved.However,the mechanism has not been studied from the perspective of root growth and water absorption.Therefore,in this experiment,five dryland winter wheat varieties of different ages in the Loess Plateau were used as materials to study their root morphology and anatomical structure,aquaporin expression and hydraulic conductivity changes,and to explore the water absorption capacity of dryland wheat varieties in the replacement of the roots.The change mechanism provides theoretical basis and guidance for dryland winter wheat breeding and optimization of root system architecture and root function to achieve high yield and high efficiency of dryland winter wheat.Main research results:(1)There are obvious differences between the total root length and the primary root length in wheat variety replacement,and there is a slight upward trend in general.Under drought stress conditions,the main radicle,primary root,secondary root and total root length of each variety increased.Under normal water conditions,the root morphological characteristics of the five wheat varieties changed little with the trend of variety replacement.The total root surface area,root dry weight,aerial part dry weight,and root-to-shoot ratio of the five varieties gradually increased with the change of ages.high.Changhan 58 has higher total root length,total surface area and smaller root-to-shoot ratio than other varieties,and shows better adaptability under drought stress.(2)In the cultivar replacement,the root diameter and the thickness of the cortex have obvious differences between cultivars,and the overall trend is increasing.Drought induces corkification of the inner and outer cortex,making this trend more obvious.Under the two moisture conditions,the diameter of the xylem vessel decreases with the change of varieties,and the ratio of the diameter of the xylem vessel to the root diameter decreases overall.The smaller the diameter of the root xylem vessel,the greater the axial resistance to water flow,and the smaller the diameter of the xylem vessel It is beneficial for wheat to use the soil moisture in the later stage more effectively.(3)With the change of wheat varieties,the relative expression of TaPIP1;2 and TaPIP2;5under normal water conditions has an upward trend,indicating that wheat roots increase its membrane density by increasing the expression of aquaporin and promote Wheat roots absorb water.The drought threat inhibited the expression of TaPIP1;2 and TaPIP2;5.The aquaporin expression of Changhan 58 was at a higher level under the two water conditions.(4)With the replacement of wheat varieties,the hydraulic conductivity of a single root gradually increased under normal water conditions,and drought stress significantly reduced the hydraulic conductivity of a single root,and there was no significant difference between different varieties.The conductivity has a tendency to decrease.The relative expression of aquaporin under drought conditions is the most important physiological parameter to control the water conductance of a single root,and the anatomical structure of the root system under normal water conditions has the strongest correlation with the water conductance.Compared with other varieties,Changhan 58 guarantees water absorption potential due to its larger root length and root to shoot ratio under water stress conditions;larger root cortex thickness,root diameter,and smaller xylem ducts increase the resistance to water transport;The higher expression of aquaporin provides a relatively stable root water absorption capacity and is a better drought-resistant variety.